Feasting, Fasting, Insulin, HGH, Fat and Livers: A Roundup

I read two marvelously detailed, researched, informative and interesting blog post today that I had somehow missed. They are both by the same reader and commenter here, Robert McLeod, who as a physicist is pretty damn good at math and plain old logic. As an example, here's a kinda fun, tongue-in-cheek look at saturated fat epidemiology.

I must warn you that these are pretty advanced. However, if you truly want to understand what's going on with fat accumulation and fat loss, I can think of no better way to spend a bit of time. The comments on both posts are good, too.

The first of these is: Feast and Fast: the dichotomy of insulin and growth hormone. In a nutshell, he explains in brief, but in excellent detail just how insulin keeps your fat locked in and accumulates more, and just how growth hormone preserves your organs and muscles and releases your fat for use by the body. Here's what most of you already know: it's the high carbohydrate that keeps insulin elevated and makes you fatter and fatter with each passing year (you know, the diet recommended by the "experts"). But, did you also know the rest?

So, to review, insulin is the hormone responsible for regulating the metabolism of glucose and most amino acids (exceptions are lysine and leucine) derived from the protein in your diet that are converted to glucose for the purpose of fuel (Gröschl et al., 2003). High levels of insulin also prevent your muscles from absorbing fatty acids in the blood: the body prefers to burn the low-energy density carbohydrates first and hold onto the superior fatty acids for lean times. A person with high levels of insulin in their blood is said to be in the feasted state.

The opposite to the feasted state is the fasted state. The hormone that characterizes the fasted state is growth hormone (review: Møller and Jørgensen, 2009). The general course of progressing from feasted to fasted goes something like this:

  1. You eat a meal with carbohydrates and protein. Digestion occurs over the course of several hours and insulin levels rise in response to the absorption of these macronutrients.
  2. Insulin sensitive tissues absorb glucose from the blood-stream. Glucagon, a second-tier hormone, causes the liver to break down the glycogen it stores into glucose, releasing it into the blood. This slows the rate at which insulin drops.
  3. Insulin continues to drop as the liver's supply of carbohydrate is reduced. Ghrelin (which I'll discuss later) is produced, which promotes appetite and the production of growth hormone. If the increase in appetite caused by ghrelin causes you to eat, you go back to stage 1. Otherwise, you make the transition into the fasted state as GH levels rise and blood sugar levels drop (Roth et al., 1963).

Growth hormone is basically the hormone that controls when your adipose (fat) tissues release fatty acids to be metabolized by the rest of your body. No growth hormone, no significant fat loss.

I really encourage you to go and get all the details behind this and more. Bookmark it. What I like about it is that it suggested a few things I might modify or at least intensify. It's really nice to have solid knowledge backing up what you sense to be true and have actually experienced.

It also informs you as to how thoroughly messed up the world is in terms of diet and nutrition.

Now, onto Robert's next post: Synthesis of Fat in the Liver. This is quite an interesting post in which Robert ends up wondering if we ought not to eat carbohydrate and protein/fat in the same meal. It makes some sense to me.

But before that, Robert delivers quite good instruction on the liver's central role in metabolism, and how we get man boobs and wheat bellies.

…So what causes people to preferentially deposit fat around their mid-section rather than elsewhere? In researching non-alcoholic fatty liver disease, I came across the following paragraph by Postic and Girard (2008, free access), which I think is instructive:

Insulin is essential for the maintenance of carbohydrate and lipid homeostasis. Insulin is secreted by pancreatic β cells in response to increased circulating levels of glucose after a meal. A large fraction of glucose absorbed from the small intestine is immediately taken up by hepatocytes [RM: liver cells], which convert it into glycogen. However, when the liver is saturated with glycogen (roughly 5% of liver mass), any additional glucose taken up by hepatocytes is shunted into pathways leading to synthesis of fatty acids, which will be esterified into TG [RM: triglycerides] to be exported to adipose tissue as very low-density lipoproteins (VLDLs). Insulin inhibits lipolysis [RM: fat burning] in adipose tissue by inhibiting hormone-sensitive lipase (HSL), the enzyme regulating FFA [free-fatty acid] release from adipose tissue (10). Therefore, from a whole-body perspective, insulin has a “fat-sparing” effect by driving most cells to preferentially oxidize carbohydrates instead of fatty acids for energy. Insulin also regulates glucose homeostasis at many sites, reducing hepatic glucose production (HGP) (via decreased glucose biosynthesis [gluconeogenesis] and glycogen breakdown [glycogenolysis]) and increasing the rate of glucose uptake, primarily into skeletal muscle and adipose tissue.

As with the previous, I encourage you to go get the whole lesson.

Now, I had intended to immediately go into what I was going to tweak in my own approach, to see if it would work. But I have a better idea. How about all of you who are interested, go read Robert's two posts, and consider how that knowledge might change a thing or two in what you're doing.

Then, tomorrow, I'll give you my own thoughts.

Since Covid killed my Cabo San Lucas vacation-rental business in 2021, this is my day job. I can't do it without you. Memberships are $10 monthly, $20 quarterly, or $65 annually. Two premium coffees per month. Every membership helps finance this work I do, and if you like what I do, please chip in. No grandiose pitches.


  1. Chris - ZTF on April 23, 2009 at 22:17

    Very interesting and nicely put down. This is why people get there best results in Fat Loss and Muscle gain during fasted workouts. I remember years ago when I first got into training, I had no clue about nutrition etc but I would always go for fasted runs and pushups in the morning after some coffee…… Would make a world of difference in my results even though I was eating like crap back then… When I dropped the AM workouts the diet would catch up with me and cause weight gain (Fat gain) thankfully now we have the diet dialed in!

  2. Skyler Tanner on April 23, 2009 at 18:12

    Good stuff, though I'm of the opinion that GH gets far too much credit when it comes to fat loss/muscle gain. An optimizer, maybe, but not a panacea.

  3. Patrik on April 24, 2009 at 11:33

    Great work Richard and Robert. Keep it up.

  4. Robert M. on April 24, 2009 at 12:07


    Thanks for the kind words.


    I don't think there's any doubt that growth hormone is the fat-metabolism hormone in the same way that insulin is the glucose-metabolism hormone. However, the name 'growth hormone' is misleading and a legacy of past-research. GH, as far as I can tell, doesn't build muscle or bone on its own. It may up-regulate those that do.

    It's common in biology for one molecule to have two or three different names, all arrived at by parallel lines of research that didn't collaborate until someone realized they were the same thing at a later date.

  5. Katelyn on April 24, 2009 at 12:45

    That is exactly why I am ZC (zero carb). See Zeroing in on Health Blog . I eat zero carbohydrates (excepting the .4 gm in each egg) and I feel so energetic. There is no need for carbohydrates. I would encourage everyone to go ZC.

  6. Skyler Tanner on April 25, 2009 at 05:38

    Hey Robert,

    You'll get no argument from me. I just see many people doing X to increase GH and all I can do is reference studies where they're injecting athletes and elderly with large doses and not improving muscle or losing fat. If suprapsychological-levels of injection isn't going to do it, why should I care about the 15' spike after a workout?

  7. Skyler Tanner on April 25, 2009 at 09:42

    That might just be the case, though I'm at work and don't have access to my stockpile of studies regarding GH and muscle mass. I seem to recall studies that injected in a caloric deficit, which isn't the same as a fast but give an idea of the ability of GH to hold onto tissue. I'll confirm this later.

  8. Skyler Tanner on April 25, 2009 at 13:41


    I can link you to many studies, but this stands out to me:

    2: Exerc Sport Sci Rev. 1994;22:285-312.

    Growth hormone effects on metabolism, body composition, muscle mass, and

    Yarasheski KE.

    Metabolism Division, Washington University School of Medicine, St. Louis,

    Even in catabolic or GH-deficient populations, GH treatment provides only modest
    increments in nitrogen retention, muscle size, strength, and exercise capacity.
    Further, the side effects of GH treatment (water retention, carpal tunnel
    compression, insulin resistance) would be a detriment, rather than an aid, to
    athletic performance.

    So suprapsychological levels actually decrease insulin sensitivity, don't seem to do anything for muscle tissue, and has a host of side effects. This is interesting as one would think that, if GH does some good whilst fasted, that extra nutrients would multiply that effect but that hasn't panned out in research.

  9. Richard Nikoley on April 25, 2009 at 08:54

    Could it be that the most important element of GH then is sparing lean tissue in a fasted state, so that fat is metabolized instead?

  10. Katelyn on April 25, 2009 at 17:58

    Richard: I love reading your blog. I would love for you to do this experiment: go ZC for 30 days. Meat and eggs ONLY. I think you'll love it and never want to return to including starches and fruits and veggies and other wastes of time. Just eat all the fatty meat that you want, eat eggs and you can use butter / lard; any animal fats.

  11. Richard Nikoley on April 25, 2009 at 11:53

    I agree the ZC can be healthful. Look no farther than the Inuit. I am less convinced its optimal.

  12. Richard Nikoley on April 25, 2009 at 18:27

    But Katelyn, I do eat all of the fatty meat and eggs I want, and probably then some. I'm doing just fine, and I _know_ what I'm doing.

    Thanks, luv, and no criticism whatsoever of your individual path.

  13. Katelyn on April 26, 2009 at 18:51

    No problem. I just think you'd love the convenience and satiety benefits. I used to be a vegetarian! I can't believe I used to eat grains and soy and fruits. Ew ;)

    I love your enthusiasm in your blog. It's a joy to read.

  14. Pauline on July 7, 2009 at 02:49

    Wow, these are both fascinating articles to read, I will take time to re-read and absorb. Experimenting with Intermittent Fasting, I can manage 18 to 20 hours no problem, anything beyond my blood sugar is too low. I think women's bodies deal differently with IF. If I do fast too often, my appetite gets confused (and so does my brain). Trying to work on simple principle of extending the fasting state between meals on a regular basis, ie 14-18 hours before eating.

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